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<body>
<details id="dt1"></details>
<details id="dt1c" open></details>
<details id="dt2"><summary>summary 2</summary></details>
<details id="dt2c" open><summary>summary 2</summary></details>
<details id="dt3"><summary>summary 1</summary></details>
<details id="dt3c" open><summary>summary 1</summary></details>
<details id="dt4" open></details>
<details id="dt4c"></details>
<details id="dt5" open><summary>summary 2</summary></details>
<details id="dt5c"><summary>summary 2</summary></details>
<details id="dt6" open><summary>summary 1</summary></details>
<details id="dt6c"><summary>summary 1</summary></details>
</body>
